Sexual agglutination is the first step in the conjugation process in yeasts. The specificity for cellular recognition is determined by cell surface glycoproteins that are complementary. These glycoprotein agglutination factors may be located on surface filaments. Neither sex-specific glycoprotein mating factor is synthesized in the diploid hybrid. The overall objectives of the total project are to discover the genetic control mechanisms governing the synthesis of the haploid recognition factors and their repression in the diploid of the yeast Hansenula wingei. The goals set for the current year are to publish a preliminary genetic map of this yeast and to isolate mutants affecting the mating type locus. The first mutants to be sought will be diploids that are temperature-sensitive for repression of sexual agglutination. These mutations will be mappd to determine whether the mating type locus also governs the repression of haloid functions in diploid. Ultrastructural changes in these mutants will be monitored to help localize the recognition factors on the cell surface filaments. Cell surface matrix will also be investigated in parallel studies with the yeast Candida albicans in an attempt to identify cell surface factors involved in yeast flocculation, adherence to animal cells and antigenicity.